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Increased separation of food waste driven by the European Circular Economy Action Plan will create a need for establishing new treatment plants that can turn waste resources into high value products. This paper presents a real example of how life cycle assessment was used as decision support when establishing a new anaerobic digestion plant in Norway. The aim of the paper is to investigate the accuracy of the results of the predictive study performed before the plant was built by comparing them with results from the operation of the plant. The comparative assessment revealed that both the burdens and avoided emissions were underestimated. The production volume of upgraded biogas as a fuel for transport was higher than anticipated, resulting in a higher benefit than expected associated with substitution of diesel. Conversely, the impacts from transport and from the anaerobic digestion process were higher than forecasted. In total the net results from the predictive study were within an acceptable range compared with results based on real data.

The aim of the paper is to make an x-ray of the potential of biological waste collection for the production of biofuels and fertilizers in Romania. It presents the existing legislative framework on bio-waste management as well as recycling technologies. A case study on the evaluation of the potential for selective collection of bio-waste for its anaerobic digestion is described.

Water pollution has become a serious issue of this century due to increased industrialization. Several methods have been adopted to tackle this issue, including adsorption by activated carbon (AC). Conventional sources of AC preparation are costly and non-renewable as well. Several fruit and agricultural wastes have characteristics to become sustainable feedstock for AC preparation. This study aims to prepare cost effective AC from sustainable raw material, cow dung. The preparation has been analyzed and optimized by utilizing central composite design (CCD). The effect of activation temperature, time, and impregnation ratio (IR) on responses of percent yield ( R1) and percent pesticide removal (R2) has been analyzed. Quadratic models have been suggested with R2, adjusted R2, and predicted R2 values of 0.98, 0.96, 0.89 for R1, and 0.97, 0.94, 0.87 for R2, respectively. Activation temperature and KOH/Feedstock ratio significantly influence the yield and pesticide removal. Optimized conditions of activation temperature, KOH/Feedstock ratio, and activation time are 708.07 ?C, 1.22 and 0.66 h, respectively. These conditions produced 14.78% yield and 89.18% pesticide removal. SEM and BET analysis of optimized AC also confirmed porosity development and large surface area availability due to activation process. Findings of this study suggest that cow dung can be used to prepare low-cost AC for pesticide removal from aqueous solution.

Compostable plastics benefit from a favorable image among the general public, politicians and principals, in particular to selectively collect biowaste. In order to evaluate their behavior in mesophilic methanisation and their contribution to the production of biomethane, the present study compares the anaerobic biodegradability of 10 compostable plastics and 4 paper bags that can be used for the selective collection of biowaste. The results show that compostable plastics have relatively little or no anaerobic biodegradability (0 to 136 mL(CH4)/gVM) or generate an inhibition of the biological process of methanisation. Comparatively, the 4 paper bags tested showed methanogenic potentials of 214 to 313 mL(CH4)/gVM and standard production kinetics. Moreover, the co-digestion of compostable plastics with biowaste seems to promote the anaerobic biodegradability of materials despite a lag phase at the initiation of digestion. Maintaining the physical integrity of compostable plastics after methanisation could present an operational risk related to their accumulation in the digester as well as the generation of (micro) plastics in the digestates. Thus, in industrial context, compostable plastics must be, in the same way as conventional plastics, withdrawn from fermentable organic matter, upstream of digestion, by mechanical pre-treatment of the incoming deposit., Les plastiques compostables bénéficient d’une image favorable auprès du grand public, des politiques et des donneurs d’ordre, notamment pour collecter sélectivement les biodéchets. Afin d’évaluer leur comportement en méthanisation mésophile et leur contribution à la production de biométhane, la présente étude compare la biodégradabilité anaérobie de 10 plastiques compostables et de 4 sacs en papier utilisables pour la collecte sélective de biodéchets. Les résultats montrent que les plastiques compostables ont une biodégradabilité anaérobie relativement faible ou nulle (0 à 136 mL(CH4)/gMV) ou génèrent une inhibition du procédé biologique de méthanisation. Comparativement, les 4 sacs en papier testés ont présenté des potentiels méthanogènes de 214 à 313 mL(CH4)/gMV et des cinétiques standards de production. Par ailleurs, la co-digestion de certains plastiques compostables avec des biodéchets semble favoriser leur biodégradabilité anaérobie malgré une phase de latence à l’initiation de la digestion. Le maintien de l’intégrité physique des plastiques compostables constaté après méthanisation peut présenter un risque opérationnel relatif à leur accumulation dans le digesteur ainsi que la génération de (micro)plastiques dans les digestats. Ainsi, les plastiques compostables doivent être, au même titre que les plastiques conventionnels, soutirés de la matière organique fermentescible, en amont de la digestion, par prétraitement mécanique du gisement entrant.

A persistent topic of the anaerobic digestion of biowaste is the efficient use of co-substrates. According to Renewable Energy Sources Act the co-substrate input is limited to 10 percent of the average daily substrate feed in Germany. In this concern, the primary focus of this paper is to understand the suitability of crude glycerol in anaerobic digestion of biowaste. Two identical lab-scale anaerobic digester units were added with crude glycerol, and each unit was equipped with four identical fermenters. Unit A was fed with an average organic loading rate of 4.5 kg VS m&minus, 3 d&minus, 1, and the average organic loading rate of unit B was set at 5.5 kg VS m&minus, 1. The share of crude glycerol in the total feed was 0.77 percent of the fresh matter. The abort criterion is a ratio of the volatile organic acids and buffer capacity (FOS/TAC) in the fermenter above 1.2. The abort criterion was reached after 16 days. In summary, the results lead us to the conclusion crude glycerol is not suitable as a co-substrate for anaerobic digestion for several reasons.

Waste solid residue from the hydrothermal extraction of pectin derived from sugar beet pulp was used as feedstock in the production of 5-hydroxymethylfurfural (5-HMF). The depolymerization of pectin-free sugar beet pulp (PF-SBP) to monosaccharides and their dehydration to 5-HMF were conducted in subcritical water using a batch reactor. The experimental design methodology was used in order to model the hydrothermal process and to optimize the operational parameters of the reaction, namely temperature and holding time. These parameters are required to achieve the highest yield of 5-HMF. The model predicts, in good agreement with experimental results (R2 = 0.935), an optimal yield of 5-HMF (of approximately 38% in relation to the cellulosic fraction content in the PF-SBP) at a temperature of 192.5 °C and a holding time of about 51.2 min. 5-HMF was successfully isolated from the reaction mixture using the liquid–liquid extraction method. The results are suitable for industrial upscaling and may become an incentive to introduce a new, environmentally friendly, uncomplicated, and efficient waste treatment method. The method would be used to treat products from the sugar refining industry, the treatment of which has proven to be problematic until now.

This paper aims to analyze the economic feasibility of generating a novel, innovative biofuel&mdash, bioenergy&mdash, obtained from deposit bio-components by means of a pilot installation of sewage sludge bio-conversion. Fuel produced from sewage sludge biomass bears the potential of being considered a renewable energy source. In the present study, 23 bioconversion cycles were conducted taking into consideration the different contents, types of high carbohydrate additives, moisture content of the mixture as well as the shape of the bed elements. The biofuel was produced using post fermentation sewage sludge for industrial energy and heat generation. Based on the presented research it was concluded that the composite biofuel can be co-combusted with hard coal with the optimal percentage share within the range of 20&ndash, 30% w/w. Sewage sludge stabilized by means of anaerobic digestion carried out in closed fermentation chambers is the final product. The average values of the CO2, CO, NO, NOx and SO2 concentrations in flue gas from co-combustion of a bioconversion product (20% w/w) and coal were 5.43%, 1903 ppm, 300 ppm, 303 ppm and 179 ppm, respectively. In total, within a period of 4.5 years of the plant operation, 1853 Mg of fuel was produced and successfully co-combusted with coal in a power plant. The research demonstrated that in the waste water treatment sector there exists energy potential in terms of calorific value which translates into tangible benefits both in the context of energy generation as well as environmental protection. Over 700,000 Mg of bio-sewage sludge is generated annually in Poland. According to findings of the study presented in the paper, the proposed solution could give 970,000 Mg of dry mass of biomass qualified as energy biomass replacing fossil fuels.

The paper presents, for the first time, the results of fuel characteristics of biochars from torrefaction (a.k.a., roasting or low-temperature pyrolysis) of elephant dung (manure). Elephant dung could be processed and valorized by torrefaction to produce fuel with improved qualities for cooking. The work aimed to examine the possibility of using torrefaction to (1) valorize elephant waste and to (2) determine the impact of technological parameters (temperature and duration of the torrefaction process) on the waste conversion rate and fuel properties of resulting biochar (biocoal). In addition, the influence of temperature on the kinetics of the torrefaction and its energy consumption was examined. The lab-scale experiment was based on the production of biocoals at six temperatures (200–300 °C; 20 °C interval) and three process durations of the torrefaction (20, 40, 60 min). The generated biocoals were characterized in terms of moisture content, organic matter, ash, and higher heating values. In addition, thermogravimetric and differential scanning calorimetry analyses were also used for process kinetics assessment. The results show that torrefaction is a feasible method for elephant dung valorization and it could be used as fuel. The process temperature ranging from 200 to 260 °C did not affect the key fuel properties (high heating value, HHV, HHVdaf, regardless of the process duration), i.e., important practical information for proposed low-tech applications. However, the higher heating values of the biocoal decreased above 260 °C. Further research is needed regarding the torrefaction of elephant dung focused on scaling up, techno-economic analyses, and the possibility of improving access to reliable energy sources in rural areas.

As the world’s population and urbanization have significantly increased in the past few decades, the generation of municipal solid waste has accelerated on global scale. The biowaste disposal, which is an integral part of municipal waste, leads to leachate production. These kinds of wastewater are characterized by complex composition with very high concentrations of organic and inorganic pollution substances and toxicity, which may have harmful impact on the environment. This study investigated the physico-chemical and biological characterization of leachate from biowaste. The experiments were conducted in batch performance with initial concentration of leachate, expressed as chemical oxygen demand, 12.21 ± 0.46 g O2/L and pH value 4.05 ± 0.13. Obtained results showed that leachate from biowaste have high value of chemical oxygen demand, toxicity and low pH. Overall efficiency of the process of aerobic biodegradation was 89 %. The abundance of viable bacterial cells and development of activated sludge flocs during the experiment confirmed the biodegradability of leachate from biowaste.

In comparison to lignocellulosic biomass, which is suitable for thermo-chemical valorization, the organic fraction of municipal solid waste (OFMSW) is mainly treated via composting or anaerobic digestion (AD). An efficient utilization of OFMSW is difficult due to variations in its composition. Based on the characteristics of OFMSW, hydrothermal treatment (HTT) experiments at temperatures < 200 °C as an alternative OFMSW-processing were evaluated in this study. The raw OFMSW was characterized with a dry matter (DM)-based organic dry matter (oDM) content of 77.88 ± 1.37 %DM and a higher heating value (HHV) of 15,417 ± 1258 J/gDM. Through HTT at 150, 170 and 185 °C, the oDM contents as well as H/C and O/C ratios were lowered while the HHV increased up to 16,716 ± 257 J/gDM. HTT led to improved fuel properties concerning ash melting, corrosion stress and emission behavior. Negative consequences of the HTT process were higher contents of ash in the biochar as well as accumulated heavy metals. In the sense of a bioeconomy, it could be beneficial to first convert raw OFMSW into CH4 through AD followed by HTT of the AD-digestate for the generation of solid fuels and liquid products. This could increase the overall utilization efficiency of OFMSW.

The condensation-collection and quantitative analysis of bio-oil limit its component investigation and utilization. In order to find a convenient method for the analysis of bio-oil, the present study conducted an attempt for bio-oil quantitative analysis with the addition of internal standards before pyrolysis. Based on their good thermal stability, phenethyl acetate and naphthalene were selected as standards in the study and experiments were carried out to compare the effects of two added modes (adding into the biowaste before pyrolysis or adding into bio-oil after pyrolysis) on the bio-oil analysis. The results showed that both phenethyl acetate and naphthalene were mainly volatilized under testing conditions, which could be transferred into the oil with the volatile matters during biowaste pyrolysis. Through the co-pyrolysis experiments of the internal standards with lignin and cellulose, almost no interactions were found between the internal standards and such components. Furthermore, adding these standards before pyrolysis hardly affected the properties of noncondensable gas and biochar from the used biowaste samples (tobacco and sawdust waste). Compared with the bio-oil analysis results via traditional methods by adding standards into the bio-oil after pyrolysis, the results regarding the component distribution characteristics of the bio-oil were similar using the proposed method through the addition of standards before pyrolysis. Considering adequate mixing of the added standards (before pyrolysis) in the generated bio-oil, the proposed method could partly help to avoid inaccurate analysis of bio-oil components caused by incomplete collection of the pyrolytic volatiles.

Knowledge of kinetic parameters of CO production during biowaste composting is significantly important for the prediction of its course and estimation of total gas quantity. This allows increasing the control of the process, to minimize its negative impact on the environment and to protect the occupational safety of employees exposed to CO in the biowaste composting plant. For the first time, a full study of the influence of temperature and biowaste sterilization on the kinetics of CO production is presented. The lab-scale experiments used a mixture of green waste, dairy cattle manure, and sawdust in two variants: sterilized and non-sterilized samples. The process was carried out in controlled temperature reactors with measuring the concentrations of CO, O2, and CO2 every 12 h.CO production and k value increased with temperature. However, higher CO production was observed in biotic conditions between 10~50 &deg, C, suggesting the biotic CO formation and 1st-order kinetics. The abiotic (thermochemical) process was more efficiently generating CO above 50 &deg, C, described with a 0-order kinetic model. Additionally, the rate constant (k) value of CO production under biotic conditions was increasing up to a temperature of 60 &deg, C, above which a slight decrease in CO production rate was observed at 70 &deg, C. The presented results are the basis for further studies focused on the feasibility of (1) the mitigation and (2) valorization of CO production during the biowaste biostabilization are warranted.

The world is confronted with the depletion of natural resources due to their unsustainable use and the increasing size of populations. In this context, the efficient use of by-products, residues and wastes generated from agro-industrial and food processing opens the perspective for a wide range of benefits. In particular, legume residues are produced yearly in very large amounts and may represent an interesting source of plant proteins that contribute to satisfying the steadily increasing global protein demand. Innovative biorefinery extraction cascades may also enable the recovery of further bioactive molecules and fibers from these insufficiently tapped biomass streams. This review article gives a summary of the potential for the valorization of legume residual streams resulting from agro-industrial processing and more particularly for pea, green bean and chickpea by-products/wastes. Valuable information on the annual production volumes, geographical origin and state-of-the-art technologies for the extraction of proteins, fibers and other bioactive molecules from this source of biomass, is exhaustively listed and discussed. Finally, promising applications, already using the recovered fractions from pea, bean and chickpea residues for the formulation of feed, food, cosmetic and packaging products, are listed and discussed.

This study presents a complete characterization of the residual materials found in fruit and vegetable markets and their adaptability to be treated by anaerobic digestion with the aim of generating biogas as a new and renewable energy source. It has been determined that these substrates are perfectly suitable to be treated by anaerobic digestion, being rich in simple carbohydrates, with a high content of moisture and solids (total and volatile), which makes it a substrate of easy solubilization and with a great amount of matter directly accessible to the microorganisms responsible for anaerobic degradation. The process develops smoothly, with a slight release of acidic elements, but without impact by the development of the buffer effect by ammonia. In addition, a phenomenon of digestion is observed in two phases, indicating that despite the particulateing of the substrate, it manages to digest the organic matter directly accessible and the inaccessible. In numerical terms, 100 g of residue V produce 913.282 NmL of biogas, of which 289.333 NmL correspond to methane. The disintegration constant is 0.200 days&minus, 1, with 16,045% of the substrate degraded. As an innovation, the hydrogen generated in the process has been used as an indicator of the stability and development of the process. Accompanied by a statistical analysis and mathematical adjustments, it is possible to characterize in depth the process and its evolution, determining that the degradation is fast, with a rapid and stable hydrolysis.

One of the environmental solutions employed in order to achieve circular economy goals is methane fermentation—a technology that is beneficial both for the stabilization and reduction of organic waste and for alternative energy generation. The article presents the results of research aimed at determining the biogas and methane potential of bio-waste which has been pre-thermally disintegrated, and determining the influence of variable process parameters of disintegration on the kinetics of fermentation. A first-order kinetic model was used to describe the fermentation as well as two mathematical models: logistic and Gompertz. It has been found that process parameters such as time (0.5, 1 and 2 h) and temperature (between 55 to 175 °C) have a significant effect on the solubilization efficiency of the bio-waste. The methane fermentation of thermally disintegrated bio-waste showed that the highest biogas potential is characterized by samples treated, respectively, for 0.5 h at 155 °C and for 2 h at 175 °C. The best match for the experimental data of biogas production from disintegrated substrates was demonstrated for the Gompertz model.

Novel nanocomposite-based fertilizers produced through intelligent disposal of an abundant carbon-reach biological waste product, i.e. poultry feathers, will play an increasingly important role in sustaining global economy. Affordable, efficient, and sustainable, these fertilizer platforms derived from low or even negative value products provide a competitive alternative to conventional chemical agents. In this work, bio-fertilizer nanocomposites are fabricated from urea and keratin derived from feathers, the primary negative value by-products of poultry industry, and loaded into sustainable matrix, i.e. wood chips for sustained nutrient release. Urea-coated nanokeratin composites retain a significant fraction of the extracted organic and inorganic nutrients, and application of the loaded wood chips on the soil led to a significant improvement in germination rate, height of plant and number of leaves of cowpea compared to using urea alone, attributed to sustained release of nitrogen from the composite that prevented over-fertilization. Presence of disulphide bonds in the nanocomposite enables more efficient degradation of nanokeratin by soil microbes, providing a steady supply of essential nutrients like carbon, sulphur and nitrogen to plants. Our findings described in this communication suggest that nanokeratin-loaded wood chips may provide an efficient environmentally friendly strategy for improving soil fertility without the release of nitrous oxide, an anthropogenic greenhouse gas known to trap 300 times more heat than CO2.

A great amount of biowastes, comprising byproducts and biomass wastes, is originated yearly from the agri-food industry. These biowastes are commonly rich in proteins and polysaccharides and are mainly discarded or used for animal feeding. As regulations aim to shift from a fossil-based to a bio-based circular economy model, biowastes are also being employed for producing bio-based materials. This may involve their use in high-value applications and therefore a remarkable revalorization of those resources. The present review summarizes the main sources of protein from biowastes and co-products of the agri-food industry (i.e., wheat gluten, potato, zein, soy, rapeseed, sunflower, protein, casein, whey, blood, gelatin, collagen, keratin, and algae protein concentrates), assessing the bioplastic application (i.e., food packaging and coating, controlled release of active agents, absorbent and superabsorbent materials, agriculture, and scaffolds) for which they have been more extensively produced. The most common wet and dry processes to produce protein-based materials are also described (i.e., compression molding, injection molding, extrusion, 3D-printing, casting, and electrospinning), as well as the main characterization techniques (i.e., mechanical and rheological properties, tensile strength tests, rheological tests, thermal characterization, and optical properties). In this sense, the strategy of producing materials from biowastes to be used in agricultural applications, which converge with the zero-waste approach, seems to be remarkably attractive from a sustainability prospect (including environmental, economic, and social angles). This approach allows envisioning a reduction of some of the impacts along the product life cycle, contributing to tackling the transition toward a circular economy.

The aim of this work was to evaluate the feasibility of treating fruit and vegetable waste from a municipal market in a full-scale anaerobic digester with minimum implementation and operational costs, i.e. withoutpre-treatment, clean water consumption, active heating or mixing. For this purpose, a 13.9 m3digester that forces the submersion of solids, gains heat through solar radiation and recirculates effluent was monitored during one year of real operational and weather conditions in Bolivia. The digester was initially loaded with cow rumen (inoculum source), and after eight weeks with only fruit and vegetable waste. The digester operated at anorganic loading rate(OLR) of 1 kgVS/(m3d). The normalized specificbiogas productionaveraged 0.26 m3/kgVS and increased to 0.34 m3/kgVS when OLR was halved to 0.57 kgVS/(m3d), while the passive solar design allowed an average digester temperature of 21 °C (4 °C above the average ambient temperature).

The results of the use of the domestic biowaste drying method forthe effective dehydration of the OFHMSW and the production oflignocellulosic biomass from this waste fraction are presented within thisarticle. It presents the methodology and results produced from the firstlaboratory operation of a prototype household waste dehydration unit for thedrying of household biowaste at source through the effective removal of itswater content by using the heated air-drying process. The use of domesticdehydration technique revealed the substantial mass reduction that reached amaximum of 78%w/w, while the final product’s carbohydrate content andsuggests its further use to produce biobased chemicals and bioenergy.39.99%w/w of the target material, more than 40%w/w of the material may beconverted into sugars through fermentation and from there to ethanol.Moreover, 36.11 of the already existing sugars have the potential to be directlyfermented to ethanol. Finally, considering a cost of 0.071 euro/kWh which isthe mean value cost per kWh for the Greek household and energy consumptionof 1,001–1,200 kWh which is also the average consumption of the Greekhousehold, the maximum monthly cost for a family and a 24h operation wascalculated to be 7.2 euros.

This work reports the demineralisation of soluble biorganic hyrolysates (SBOs) obtained from three materials sampled from a municipal biowaste treatment plant. The SBOs contain mineral and organic matter. They are promising bio‐based multipurpose products due to their properties as biosurfactants, chemicals for the manufacture of plastics, and fertilizers for plant growth. Demineralisation of SBOs was carried out by HCl ion exchange and HF washing to assess its effect on the pristine product chemical composition and properties. The demineralized products (SBOs‐DM) were characterized by elemental analysis, potentiometric titration, 13C‐NMR spectroscopy and surface tension measurements. They were compared with pristine SBOs. The following results were obtained: ash content 0.2‐1.1% in SBOs‐DM vs. 15–28% in pristine SBOs; lower aliphatic/aromatic C ratio in SBOs‐DM (0.8‐2.0) than in pristine SBOs (1.3‐3.4); higher critical (mineral free) micellar concentration for SBOs‐DM (1‐2.7 g L−1) than for pristine SBOs (1‐2.3 g L−1). The potential applications of SBOs‐DM and pristine SBOs are discussed.

In relation to the situation caused by the pandemic, which may also take place in the future, there is a need to find effective solutions to improve the economic situation of the floristry industry. The production and sale of flowers is time-consuming and long-term. Therefore, any information that causes the impossibility of selling the plants will result in a reduction of profitability or bankruptcy of such companies. Research on rationally utilizing biowaste from plant cultivation as well as unsold flowers for environmental protection and effective use of their potential as a raw material for bioenergy production were examined in this article. The aim of this study was to analyze the energetic potential of the biodegradable fraction of waste from floriculture. The trials included floricultural waste containing the stems, leaves and flowers of different species and hybrid tulips (Tulipa L.), roses (Rosa L.), sunflowers (Helianthus L.) and chrysanthemums (Dendranthema Des Moul.). Their biogas and methane production as well as heat of combustion were determined experimentally. The calorific value was calculated on the basis of results from selected floricultural waste and its chemical composition. The biogas production was tested on different levels of plant material fragmentation (chaff, macerate) in fermentation processes with two ranges of temperature (meso- and thermophilic fermentation). The presented results show that the highest calorific values were determined for dry stems of roses (18,520 kJ/kg) and sunflowers (18,030 kJ/kg). In turn, the lowest were obtained for dried chrysanthemums and tulips, for which the heating value reached 15,560 kJ/kg and 15,210 kJ/kg. In addition, based on one ton of the fresh mass of biowaste from floriculture, the largest biogas production including the control was obtained from the chrysanthemum chaff by mesophilic anaerobic digestion. Moreover, the largest volume of methane was received by thermophilic anaerobic digestion of roses. The highest content of biomethane (56.68%) was reached by thermophilic fermentation of roses. The energy production of the analyzed substrates was also calculated, based on the amount of biogas produced in the containers for anaerobic digestion. Additionally, a deep neural network model, which predicted the production of methane gas, was created. Owing to the properties of the network, the level of significance of variables used for modelling and prediction of biogas production was determined. The neural modelling process was carried out with the use of the H2O program.

The paper reports the results of a long term (310 days) pilot-scale trial where food waste as sole substrate was treated in a two-phase thermophilic anaerobic digestion process. This was optimized for concurrent hydrogen and methane production. First phase's optimization for hydrogen production was obtained recirculating the effluent coming from the methanogenic phase and without the addition of external chemicals. A drawback of such approach is the recirculation of ammonia into the first phase reactor for hydrogen production with possibility of consequent inhibition. Therefore this study was focused on the development of a control protocol based on ammonia concentration. The first part of this paper illustrates how the use of a variable recirculation flow makes possible to control the whole process, preventing the ammonia inhibition in the system. In order to lay down the groundwork for an automatic control of the process, in the second part of the study a preliminary statistical study is presented. In the latter are developed models to predict ammonia levels in system using the measure of Electrical Conductivity, Volatile Fatty Acids and Alkalinity. During steady state conditions, managed by a variable recirculation flow, the system produced a mixture of gas that met the standards for the biohythane mix with an average composition range of 7% H2, 58% CH4 and 35% CO2. The overall average specific gas production (SGP) reached 0.69 m3Biogas/kgTVS and gas production rate (GPR) of 2.78 m3/m3rd.

International audience; The long-term operation of efficient bioanodes supplied with waste-derived organics is a key challenge for using bioelectrochemical systems as a waste valorization technology. Here, we describe a simple procedure that allowed maintaining highly efficient bioanodes supplied with biowaste. Current densities up to 14.8 A/m2 were obtained with more than 40% of the electrons introduced as biowaste being recovered in the electrical circuit. Three fed-batch reactors were started at different biowaste loading rates. A decline of coulombic efficiencies between 22 and 31% was recorded depending on the reactor over the first 3 weeks of operation. A renewal procedure of the anode was thereafter implemented, which led to a recovery of initial performances. The second and the third renewal, allowed maintaining stable high level performances with coulombic efficiency of approximately 40% over at least 3 weeks. Electroactive biofilm dynamics were monitored using 16S rRNA-gene amplicon sequencing. Retrieved sequences were dominated by Geobacter sulfurreducens-related reads (37% of total sequences), which proportion however varied along the experiment. Interestingly, sequences affiliated to various Bacteroidetes groups were also abundant, suggesting an adaptation of the anodic biofilm to the degradation of biowaste through metabolic interactions between microbial community members.

This work evaluated the use of different external carbon sources to promote the via-nitrite nutrient removal from anaerobic effluents. The carbon sources consisted of fermentation liquid produced from the organic fraction of municipal solid waste (OFMSW FL), drainage liquid produced from OFMSW, fermentation liquid produced from vegetable and fruit waste (VFW FL) and acetic acid. Denitritation and phosphorus uptake via nitrite were evaluated in two sequencing batch reactors, one treating the anaerobic supernatant produced from the co-digestion of OFMSW and activated sludge (highly nitrogenous anaerobic effluent – HNAE), and the other one treating the weakly nitrogenous anaerobic effluent (WNAE) from an upflow anaerobic sludge blanket reactor. The use of OFMSW FL to treat HNAE resulted in high nitrite (27 mgN/(gVSS·h) (VSS – volatile suspended solids) and phosphate uptake (15 mgP/gVSS·h). In the WNAE, nutrient kinetics were much slower. The use of acetic acid and VFW FL performed poorly, while the use of OFMSW FL, which was rich in butyric acid and propionic acid, resulted in significant nutrient removal (7 mgN/gVSS·h and 6 mgP/gVSS·h). The economic evaluation showed that the use of OFMSW FL is a less expensive option than the acetic acid use.

Lab-scale experiments were performed and a mechanistic model was developed to simulate the solid state digestion of biowaste in a batch reactor. Both experiments and model showed that the substrate-seed mixing degree and leachate recirculation rate have a strong effect on the reactor performance. This is due to mass transport limitations of volatile fatty acids (VFA) within the biowaste-seed bed. In that case two regions are developed in the digester, so-called acidogenic and methanogenic pockets. Limitations in mass transport will prevent irreversible acidification during start-up of the reactor because whereas high VFA concentration is met in the fresh waste pockets, the VFA concentration in the methanogenic pockets will remain low. However, accumulation of VFA in the acidogenic pockets will reduce the hydrolysis rate of biowaste due to inhibition by VFA. Moreover, experiments and simulations showed that the reactor performance can be improved by varying the leachate recirculation rate or applying sequential batch operation.